Method of and apparatus for heat processing particulate solids



Nov. 28, 1961 D. w. ROBINSON METHOD oP AND APPARATUS FoP HEAT PROCESSINGPARTICULATE SOLIDS 2 Sheets-Sheet l Filed Aug. 29, 1958 NOV 28, 1961 WROBINSON 3,010,911

D. METHOD OF AND APPARATUS FOR HEAT PROCESSING PARTICULATE SOLIDS FiledAug. 29, 1958 2 Sheets-Sheet 2 States The present invention relates toan improved method of and apparatus for heat processing particulatesolids, and especially for expanding thermally expandible minerals, suchas vermiculite and perlite.

Vermiculite, one material to which the present invention has particularapplication, is a micaceous mineral containing water of crystallizationbetween its many layers. It has long been known that particles of thismineral, when adequately heated to cause the water 4to turn to steam,will expand orbe exfoliated, and that the resulting product is usefulfor a very broad range of purposes. In view of the usefulness of theexfoliated product, much effort has been expended in providing7 furnacesfor exfoliating or expanding the raw mineral. Through the course ofyears, a generally approved type of furnace has evolved comprising avertical column, burner means in the column, usually adjacent its top,and means adjacent the burner for introducing the mineral into thecolumn, the mineral being exposed to the burner flame and in thepreferred form of furnace gravitating through the column with theproducts of combustion, during which time its expansion is completed,and being collected in a bagging hopper or the like provided at thebottom of the column. Many other types of furnaces have also beenproposed, including a general inversion of that described and generallyhorizontal installations. In all types, however, it is an object, atleast in the modern art, to subject the mineral to an exceedingly sharprise in temperature since the degree of expansion, which occurs only inthe dimension normal to the face of the flakes or layers, issubstantially directly proportional to the rapidity of ltemperaturechange of the particle. The faster the change, the greater the degree ofexpansion; and the greater the degree of expansion, absent over-heating,the lower the bulk density and the better the quality of the product.

In the expanding or heat treating furnace, care must be exercised toavoid over-heating of the mineral particles, and yet the particles mustbe uniformly heated if a consistent product is to be produced. Relativeto overheating, vermiculite may fuse at about 1900-2400 degrees F. andbecome a substantially useless product. Also, over-heating results inclinkering oragglomeration of the mineral in the furnace, which ishighly objectionable as it reduces furnace eiciency, creates aprogressively worsening condition, results in non-uniform heat treatmentof the entering particles, and causes frequent shutdown of the process.This has been a source of great trouble in prior proposals in the art.Also, prior art furnaces have suffered the disadvantages of relativelyshort life due to burning out of the refractory lining of the expansionchamber.

The object of the present invention is to provide an improved method ofand improved apparatus for heat processing particulate solids, andespecially for expanding vermiculite, perlite and mixtures ofvermiculite and perlite, which overcome the above stated disadvantages,cause uniform heating of the particles, eliminate overheating,clinkering and agglomeration, produce a better quality product of lowerbulk density and uniform characteristics, and increase' the service lifeof the furnace.

In particular, it is an object of the invention to provide an improvedmethod of heat processing particulate solids characterized lby the stepof substantially enclosing the source of heat in an encircling shroud orcurtain of the particles being processed.

Another object of the invention is the provision of an improved methodof heat processing particulate solids comprising the steps ofintroducing the solid particles'in the form of a tubular curtain betweenthe flame of a heat producing burner and the wall of the furnace inwhich the burner is disposed, and causing the particles to move in theform of said tubular curtain through the furnace in the same directionas the combustion gases of said burner.

The immediate advantages'of this process are that the particles, whichin the curtain formed thereby constitute a relatively thin layer, are(l) uniformly heated, (2) shield the wall surfaces of the furnaceagainst overheating, and (3) move freely through the furnace withoutcontacting hot surfaces on which they could form clinkers. Theseimmediate advantages in turn result in (4) production of a uniformproduct, (5) increased service life of the furnace, (6) elimination ofclinkering, (7) maintenance of high furnace eiciency over prolongedperiods of use, (8) capability of use of an exceedingly high temperaturesource of heat, the temperature of which is substantially in excess ofthe fusion temperature of the particles, thereby to subject theparticles to a sharp temperature rise of great magnitude and enhance theheat exchange process, (9) elimination of products of fusion, (l0)increased production rates, and (1l) substantially increased overallproduction of a high quality uniform product.

Moreover, it is an object of this invention, attributable at least inpart to the above stated advantages, of providing an improved method ofand improved apparatus for popping perlite by the principle of verticaldropthrough heat processing.

A further object of the invention is the provision of improved apparatusfor heat processing particulate solids comprising means for producing asource of heat in one end of a furnace, dispersion means for introducingsolid particles in the form of a tubular curtain around the source ofheat, and a nozzle encompassing the source of heat for confining thecurtain of particles to the vicinity of said source during their passagethereby.

A still further object of the invention is the provision, in a furnacefor heat processing particulate solids, of the improvement comprising aburner having a flame nozzlel discharging into the furnace adjacent oneend thereof, an ore confining nozzle disposed adjacent the outlet ofsaid flame nozzle, and a dispersion member disposedl between saidnozzles and having ports therein vopeningl adjacent the wallof saidconfining nozzle for introducing a tubular curtain of particles alongsaid wall and for causing said tubular curtain of particles to movethrough the furnace along the furnace walls, said ore confining nozzleconfining the tubular curtain of particles to the immediate vicinity ofthe flame and the Walls of the furnace maintaining the said curtain inthe immediate vicinity of the hot products of combustion of the burner,said ,curtain of particles shielding said ore confining nozzle and thewalls of the furnace from the ame andthe products of combustion,

Yet another object of the invention is to provide an improvedfurnace forheat processing particulate solids which, in its preferred embodiment,comprises an elongate vertical furnace chamber having an outlet at thelower end thereof, a burner adjacent the upper'end of the chamber havinga flame outlet of a size smaller than the chamber directed downwardtoward the chamber, an ore conv ning nozzle of a size larger than theburner outlet disposed adjacent said outlet, a dispersion memberdisposed between the burner outlet and said nozzle and having spacedports therein opening downwardly into the space between the projectionof the burner outlet and the internal wall of the nozzle, a hopper forsolid particles disposed above the chamber and said member, and aplurality of conduits extending downwardly from said hopper to saidports for supplying particles to be processed to said ports, thedispersion member causing particles gravitating therethrough, andinduced by the burner to flow therethrough, to be discharged downwardlyas a tubular curtain into the space between saidv nozzle and the iiameissuing from the burner outlet, this tubular curtain of particles inturn gravitating downwardly through the furnace chamber in substantiallyencompassing relation to the flame and the products of combustionissuing from the bu-rner outlet.

Other objects and advantages of the invention will be- Vcome apparent inthe following detailed description.

Now, in order to acquaint those skilled in the art with the manner ofpracticing my improved method and of making and using my improvedapparatus, I shall describe, in connection with the accompanyingdrawings, a preferred embodiment of my apparatus and a preferred mannerof making and using the same.

In the drawings:

FIGURE l is a front view, partly in section and partly in elevation, ofa heat processing furnace embodying the apparatus of my invention andcapable of usein practica ing Vthe method of my invention;

FIGURE 2 is a side elevation of the furnace;

FIGURE 3 is an enlarged vertical section of the improved apparatus Ihave embodied in the furnace; and

FIGURE 4 is a cross-section of said apparatus taken substantially online 4-4 of FIGURE 31.

Referring now to the drawings, I have illustrated therein a heatprocessing or expanding furnace of a generally conventional constructionwhich I have modifiedV in accordance with and for purposes of practicingthe present invention. The furnace per se includes a verticallyextendingframe I formed of standard structural steel forms and defining a tall,narrow, generally upright box. Mounted within the upper portion yof thisbox is means defining a furnace chamber 12, which means as illustratedincludes a tubular refractory lining 14, suitably built up fromrchimneybrick, a steel sheath 16 and a loose ll 1S of exfoliated vermiculitebetween the lining 14 and sheath 16. At its lower end, the chamber 12 isprovided with an outlet 20 discharging into a bagging Ahopper 22 or thelike, which is approximately twice as Wide as Athe means defining thefurnace chamber andincludes adelivery spout 24. Connected tothe spout 24is a conduit 26 establishing communication between the delivery spoutand hopper and a cyclone type dust separator 28 which is mounted in anupright position on the frame 10. Ad-

jacent the means defining the chamber 12, the furnace f includesanexhaust flue 3i) which'overlies the open portion of the hopper 22.Within the hopper, immediately below the furnace chamber and the exhaustue, the furnace also preferably includes a standard form of recuperator32.

In use of this generally known type of expanding furnace, a burneris'pr'ovided adjacent the upper end of the tubular furnace chamber 12and vermicuiite or alike mineral is introduced in particle form into theflame issu ing from the burner. The products of combustion of the burnerow downwardly through the chamber 12 and the vermiculite particlesgravitate downwardly therewith, whereby the vermiculite is heated andexfoliated in the expansion chamber 12 during its descent therethrough.The exfoliated product then gravitates into the hopper 22 l, i and isdischarged through the spout 24 into bags or railroad cars, theseparator 2S removing tine sized particles which' are'carried into theexhaust cyclone. The prod-Y ucts of combustion from the burner alsodischarge downwardly into Vthe hopper, .andfrom thence ii-ow upwardlythrough theriiue 30, the hotrgases thus making two passesV Y over thetubes of the recuperator for known purposes,

'desired objectives, especially several problems have been encountered.First, it is difiicult uniformly to heat the particles of vermiculitebeing processed, so that the exfoliated product does not have theuniformity sought after. Second, the rate of heat exchange, or therapidity of temperature increase in each particle, is not as great asdesired, so that density is higher and quality lower than that known tobe obtainable. Third, the flame and the products of combustion of theburner heat not only the vermiculite but the walls of the furnace liner.Radiation of heat from the walls has been thought to increase particleheating, but heating of the large wall surfaces to accomplish thisresult is quite ineliicient. Also this creates an exceedingly hotsurface which is contacted by the vermiculite and to which the particlesfuse, thus resulting in the accumulation of elinkers which impairfurnace efficiency. Moreover, such heating of the walls causes physicalbreeakdown of the refractory brick, whereby the chamber mustperiodically be re-built. For these several reasons, production, both asto quality and rate, has fallen considerably short of in the light ofthe critical specifications required to be met by exfoliated vermiculiteintended for the specialized uses which are rapidly being discovered.

The objects of the present invention are to overcome the stateddisadvantages of known furnaces and to provide for a high rate ofproduction of la lightweight, high grade exfoliated product ofexceptional uniformity. According to the method of the invention, theseobjectives are attained by introducing into the furnace the solidparticles to be processed in the form of a thin shroud encircling theflame aud the products of combustion of the burner and insulating thewalls of the furnace from the flame and the hot gases. The apparatusthat I prefer for practice lof my method is best illustrated in FIGURES3 and 4;

As shown, the preferred apparatus includes a high out put burner v4i)mounted in a vertical position above the chamber and having its outletor flame nozzle 42 aligned axially with and directed downwardly towardthe chamber. The burner is of a known pressure type adapted to burneither gas or oil, or 'both gas and oil, and one burner I have foundparticularly Vsuitable is the Model 4017 burner produced by ThermalResearch and Engineering Co., which burner has an output .of from about400,000 to about 2,000,000 B.t.u. per hour. The burner includes a angedhousing 44 by means of which I mount the same on a portion 46 of theframe 10 which is spaced upwardly from and overlies the chamber 12. Tothe upper side .of the frame portion 46, the burner 40 includes an airinlet 48, a gas inlet 50, and oil inlet S2 and an oil outlet 54 forsupply of fuel and combustionair to the burner, the air inlet 48suitably being connected to the outlet of the recuperator 32 for thepurpose previously mentioned. rl'he nozzle 42 of the burner 40 is formedof refractory material and constitutes the combustion charnber of theVburner, from which is discharged, in a vertically downward direction,Vashort, generally cylindrical flame as is indicated in dotted lines.

The cylindrical flame and the hot products of combustion of the burnerdischarge into an ore conlining Y Mounted betweenY andY concentricallywith the nozzles 42 and 56 is a dispersion ring or annulus 60, which isalso preferably formed of refractory material and cemented or otherwisesealed to the nozzles 42 and 56. At its lower end, the ring 60 isprovided with a flat annular surface to engage hush against the uppersurface of the nozzle 56, and its upper surface is suitably offrusto-conical shape c-onformably to receive the conical nose of the amenozzle 42. In its upper surface, the ring 60 is provided at equalcircumferential spacings with a plurality of inclined, generallyradially extending ports 62 which open downwardly into the annular spacebetween the flame and the wall of the nozzle 55, or more properly, intothe annular space between the axial projection of the burner outlet andthe wall of the ore confining nozzle. In the drawings, I have shown sixsuch ports, as being preferred, but it is apparent that more or lessports could be provided as desired, since the number of ports or vanesis not critical. Communicating axially with each of the ports is a feedpipe or conduit 64, the six pipes extending upwardly to and beingsupported by the portion 46 of the frame 10 on which the burner ismounted and defining a circle circumscribing the burner. At the upperend thereof, each pipe terminates in a coupler or fitting 66facilitating attachment thereto of secondary feed pipes or conduits.

Mounted on the frame portion d6 in upwardly extending relation theretois a standard 68 which supports a feed hopper 70 in a position above theburner and the dispersion ring. This hopper is adapted for receptionofsolid particles to be heat processed and includes a lower plate havingtherein tubular discharge stubs 72 of a number corresponding to thenumber of primary feed pipes 64. Between each stub 72 and thecorresponding fitting 56 is extended a secondary feed pipe 74 which isdetachably secured at its ends in sealed relation to the respectivefitting 66 and stub 72. In addition, the hopper 70 preferably includesvalve means (not shown) for controlling the rate of discharge ofparticles therefrom.

In use of the apparatus, the burner 40 is iirst set into operation tocause a short, generally cylindrical iiame to be directed downwardlyinto the ore confining nozzle 56 and the hot products of combustion ofthe burner to be discharged downwardly through the chamber 12 andupwardly through the flue 30, the hot gases during such passagetransferring heat through the recuperator 32 to the combustion air forthe burner. The valve means in the feed hopper 70 is then opened,whereupon solid particles are fed downwardly from the hopper through thepipes 74- and 64 to the ports 62 in the dispersion ring 60, a constantfeed of particles to the ring 60 being assured by virtue both of theforce of gravity and the inductive force created by the flamedischarging into a relatively large area and causing a venturi effect atthe ports 62. Due to this action, the ring 60 causes the solid particlesto be dispersed in an annular curtain and to be discharged in that formdownwardly into the annular space between the flame and the internalwall of the nozzle 56. Thus, the discharged particles are subjected touniform contact with the iiame as the relatively thin curtain ofparticles descends through the particle confining nozzle. Also, theincoming particles and the air induced to flow downwardly therewithserve to keep the dispersion ring relatively cool and to insulate thenozzle S6 from the flame and the hot products of combustion.Consequently, the surfaces of the ring and nozzle are not heated to suchextent as would result in fusion or clinkering of the solid particlescontacting the same. Also, the incoming particles are immediateiycontacted with an exceedingly hot liame, preferably several hundreddegrees hotter than the fusion temperature of the particles, whereby theparticles are subjected to an instantaneous temperature rise of greatwardly into and through the chamber 12 with the hot products ofcombustion from the burner, the particles mixing -with and absorbingheat from the hot gases and being further heat treated during theirpassage through the chamber 12. Due to the fact that the particlessurround the ame and move continuously with hot gases, heat transfer isprimarily between the ame and gases and the particles, whereby theparticles are subjected to optimum and uniform heat treatment, the heatproduced by the burner is most eifectively and efiiciently utilized, andexcessive heating of the walls of the nozzle 56 and chamber 12 isavoided. By virtue of the latter function, hot surfaces on which theparticles could fuse and form clinkers are eliminated and physicalbreakdown of the refractory materials of the chamber is mitigated,thereby to insure efficient operation of the furnace over exceptionallylong periods of continuous use without necessity for cleaning lorrepair. Also, due to the sharp initial rise in particle temperature uponcontact with the ame, and the primary heat exchange relationship betweenthe particles and the flame and hot products of combustion, theparticles very rapidly complete their heating cycle so that the rate of:dow of particles through the furnace may be substantially increasedover that conventionally accepted. Moreover, the coaction of theparticles and the products of combustion facilitate complete liexibilityof control, in that either fuel input or ore input, or both fuel inputand ore input, may be adjusted in order to provide the proper heattreatment cycle.

By way of more specific example, I 'will now describe the manner of useof my apparatus and the practice of my method for expanding vermiculiteore, and especially for production of No. 4 exfoliated vermiculite. Theore on which the invention is practiced is entirely conventional in allrespects, the same being mined, milled t0 controlled size and depositedin the hopper 70 in conventional manners and to conventionalspecifications. The ore used is a natural equilibrium ore having amoisture content from about 5% to about 12%. The ore is to -be expandedto afford a given set of characteristics which characteristics areachieved by exfoliating the particles of ore at such temperature as toproduce a predetermined percent shrinkage in the exfoliated product, allin accordance with the disclosure of the co-pending application ofGeorge E. Ziegler, Serial No. 632,275, filed January 3, 1957, now U.S.Patent No. 2,945,820, which application is assigned to the assignee ofthis application. Control of the process is effected by thermallyresponsive control means including a thermo-couple disposed in andmeasuring the temperature of the stream of particles dis? charging fromthe chamber 12, which control means is adapted to vary the rate of feedof fuel and/or raw ore to the furnace to maintain a pre-set particledischarge temperature, periodic checks being made on the percentmagnitude, which as previously stated is highly advany tageous.

After initial contact with-the ame, the annular curtain of solidparticles gravitates and is induced to iiow downshrinkage of the productto determine the accuracy of the thermal control and accommodate anynecessary adjustment thereof. In the particular example underdiscussion, the percent shrinkage of the product is to be less than 20%and a suitable initial control temperature for the No. 4 grade is 1650degrees F. v

The furnace chamber is suitably 12 inches in diameter and about l0 feetlong. The flame nozzleof the burner may then be about 5 inches indiameter, in which lcase the inner diameter of the ore confining nozzle56 is about 6.9 inches, thereby to afford a cross-sectional nozzle areaapproximately 90% greater than the cross-sectional area of the flameoutlet. 1

The burner 40 is operated to produce a flame temperature of over 2500degrees F., preferably about 3000 to 3500 degrees F., or about 1100degrees above the fusion temperature of vermiculite, and to have anoutput 'of about 1,500,000 B.t.u. per hour. The flame projects about 8inches beyond thenose of the outlet 42 and has a diameter about or moreof the diameter of the outlet. Y

Vof the. exfoliating or expanding process.

For expansion of vermiculite ore, and with the burner operating asdescribed, the ore is introduced into the furnace in the same manner asabove defined. Production of the described grade of'exfoliatedvermiculite having less than 20% shrinkage is, effected according to thepresent invention at a feed rate of approximately 3A ton of ore per hourand results in a yield of 43 to 44 fourcubic foot bags per hour of theultimate product. The yield obtainable is over 25% 'better than thatpreviously obtained and density is reduced'to between 6.8 and 7.3 poundsper cubic foot, a signiiicant reduction clearly illustrating the fasterrate of expansion and the improved quality of the product. Despite thefact that arne temperature is about i100 or more degrees hotter than thefusion temperature of the vermiculite, there is no clinkering in thefurnace and no evidence of fusion in the exfoliated product.

From test observations and samplings, it `appears that the bulk of theexpansion of the ore occurs in the upper 1A of the furnace as aconsequence of the particles being bathed in the flame. Yet, the lengthof the furnace is necessary to complete expansion to the desired percentshrinkage. Elf-Orts to decrease furnace length 'by increasing theduration of flame bathing or" the particles, and in particular by use ofa spiral flame, proved totally ineffective, and in fact disadvantageousas the spiral action caused the ore to be comminuted. In the furnace asshown and described herein, the ore is both expanded and heat treated,clinkering is eliminated and furnace life is extended indefinitely.Yield is increased substantially, the density of the product is reduced,its quality increased, and there is substantially perfect Vuniformity ofproduct. The furnace results in comparable improvement in the productionof all grades of exfoliated vermiculite, and affords the same advantages`with respect to lboth the furnace and the quality and uniformity of theresulting product.

Jn addition to the foregoing, the present invention contributessubstantially to completely automatic operation In particular, in testsVpreviously conducted, the operator set the yfurnace into operationaccording to the following sequence of operations: The combustion airblower, .oil pump, exhaust fan and separator motors were started. Thecornbustion air pressure was adjusted to 1/2 inch, oil pressure to Vl()psi., and the burner started. When the burner produced a flame, the airwas manually increased gradually to about 6' inches. After about twominutes Warmupk time, the -oil and air pressure were increased to 120p.s.i. and l inches, respectively. When the temperature in the expansionchamber came up to 1550 degrees F., the operator put the furnace onautomatic control and manually/'adjusted the fuel and air-*pressure to18() p.s.i. and 44 inches, respectively, keeping the air in excess ofthe fuel. VThis operation took about l5 seconds. The ternperatureimmediately stabilized at i650' degrees F. and no more attention wasneeded throughout the run. Comparative runs clearly reveal a greateryieldV from the furnace Von automatic operation than on `the mostcareful manual operation. Thus, the invention aordsV not onlyimprovements in the heat processing of particulate solids, but alsofacilitates fully automatic processing.

For the production of exfoliated vermiculite Vas de-V scribedihereinbfefore,l I prefer lto employ a vertically disposed furnacechamber having the burner and ore dispersion ring at the top thereof.However, it is Ventirely fea-sible that the furnace can be utilized inIan inverted posit-ion, and other positions intermediate the twoopposite vertical positions, for processing of a widevariety of solids.VIn particular, I have in mind application of myfn'iethod and apparatusto the popping horizontally andl ular aggregate, treatment of orescontaining gold and platinum, and treatment of fluid coke from petroleumproducts to 'further remove the hydrocarbons not removed in conventionequipment.

When yapplied to some of these uses, and especially when the furnace isinstalled other 'than vertically, it may be necessary in order tomaintain an annular curtain of particles in surrounding relation to thellame and products of combustion, to blast the raw particles into thefurnace by suitable means, such as pneumatic pressure. In any event, theapparatus, in its preferred form, has the basic malte-up describedherein and is capable of performing my improved method, which broadystated comprises the steps of shielding the jet of extremely hot gasescompletely with a ring or curtain of particles, and blasting both thejet and the ring of particles into a tube which allows the gases and theparticles to ow in the same direction until sufficient heat treatment ofthe particles has taken place.

In View of the foregoing, it is apparent that the objects and advantagesof this invention have been shown to be attained in a convenient,economical and practical manner. My improved method of heat processingassures uniform heat treatment of the particles in a short period oftime, and results in protecting the furnace against excessive yabuse andpreventing clinkering therein. The preferred embodiment of my appara-tusis particularly effective in performing my defined method andconstitutes a highly economical structure necessitating of perlite aloneor inmixture with vermiculite, processr of lime, reduction of removal ofsulphur ing of limestone in the production fine iron oxide Vmixed withcolte,

from sulphides, spherulizing clay particles into a granverey littlechange in existing furnaces for modification of such furnaces inaccordance with this invention.

Moreover, the apparatus and method described herein accommodate for thefirst time effective hea-t processing or expandingof perlite andmixtures of vermiculite and perlite in a vertical dropathrough furnace,thereby to increase production rates and the quality of the expandedproducts.

The apparatus specilically illustrated and described herein constitutesthe preferred physical embodiment of my invention. However, thisapparatus is capable of vvideV variation, dependent in part on use.First, the furnace chamber need not be circular in cross-section butcould be of substantially Iany geometric or non-geometricrform. The amenozzle need not be circular, nor need it have a cross-sectionalconfiguration complementary to that of the furnace chamber. In any ofthese cases, the shroud or cur-tain of particles to be processed isintroduced in generally tubular form, whether tha-t be a circular tube,a square tube, or a tube of other configuration. Moreover, the burnerneed not be disposed concentric With or'in axial align-ment with thechamber. For many uses, especially where the furnace is not vertical, itmay prove advantageous to mount the burner'eccen-trioally and/or to cantthe same relative 4to the furnace axis. It is not essential, thoughhighly preferable, to utilize a confining nozzle that is larger than theflame nozzle. For example, by appropriate dign of the burner, a damecould be produced i iaving a hot central core and a somewhat coolerperiphery and the curtain of particles could be introduced directly intothe peripheral portion of the flame around the hot core. In such case,the confining nozzle could be of the same size as the flame, and even sothe curtain of particles would effectively enclose lthe flame and shieldthe nozzle. Likewise, the furnace chamber'need not be of asize largerthanthe confining nozzle.

-Accordingly, while I have shown and described what I regard to be thepreferredrembodiment of the apparatus of my invention, and havedescribed what IV regard to be xthe preferred manner of practicing myimproved-method, it is apparent -tha-t various changes, rearrangementsVand modiiications may be made therein without departing l claim:

l. A method of expanding vermiculite, perli-te and mixtures ofvermiculite and perlite comprising the steps of vertically dropping acurtain of ore around a -heat treating llame, and confining the curtainof ore to the vicinity of and in substantially encompassing relationtothe llame and its hot products of combustion during vertical descentof the curtain of ore.

2. A method of preventing clinkering in furnaces for heat processingthermally expandable minerals, characterized by the steps of creating -adownwardly moving curtain of particles to be processed along the furnacewalls and in encompassing relation to the source heat of the furnace,and causing said particles to move at a rate maintaining an effectivetemperature gradient between the source of :heat and said walls.

3. Apparatus for heat processing particulate solids comprising a burnerhaving a ilarne nozzle, a particle conining nozzle disposed `to theoutlet side of said flame nozzle, land dispersion means between saidnozzles for introducing a curtain of the particles to be processed alongthe walls of said conning nozzle in substantially encompassing relationto the outlet of said llame nozzle.

4. Apparatus for heat processing particulate solids comprising a burnerhaving a llame nozzle, a particle coniining nozzle disposed to theoutlet side of said llame nozzle, dispersion means be-tween said nozzlesfor introducing a curtain of the particles to be processed along thewalls of said confining nozzle in substantially encompassing relation to`said name nozzle, a hopper for particles to be processed, yand conduitmeans extending from said hopper to said dispersion means.

5. Apparatus for heat processing particulate solids comprising a burnerhaving a flame nozzle, a particle conlining nozzle of a size larger thansaid llame nozzle disposed to the outlet side of said amenozzle, anddispersion means between said nozzles for introducing a curtain of theparticles to lbe processed into the space between the projection of theoutlet of said liame nozzle and the Wall of said confining nozzle.

6. In a furnace for expanding vermiculite, perlite and mixtures ofvermiculite and perlite, the improvement comprising a burner having allame nozzle discharging into the furnace, Ian ore confining nozzledisposed adjacent the outlet of said llame nozzle, and dispersion meansdisposed between said nozzles and having ports therein opening adjacentthe walls of said conlining nozzle for introducing a curtain of orealong walls.

7. ln a furnace for heat processing particulate solids, the improvementcomprising a burner having a flame nozzle of a size smaller than thefurnace discharging into one end of the furnace, a particle confiningnozzle of a size larger than said flame nozzle disposed adjacent theoutlet of said llame nozzle, and a dispersion member disposed betweensaid nozzles and having ports therein opening adjacent the walls of saidconfining nozzle for introducing a tubular curtain of particles to beprocessed along said walls in substantially encompassing relation to theheat treating lflame issuing from said llame nozzle and for causing saidtubular curtain of particles to move through the furnace along the wallsthereof in substanl@ tially encompassing relation to the hot products ofcombustion of said burner.

S. A furnace for heat processing particulate solids comprising anelongate furnace chamber having an outlet at one end thereof, a burneradjacent the other end of said chamber, said burner having a llameoutlet of a size smaller than said chamber discharging into saidchamber, a heat treating nozzle of a size larger than said burner outletdisposed adjacent said burner outlet, a dispersion member disposedbetween said burner outlet and said nozzle and having ports thereinopening into the space between the axial projection of said burneroutlet and the wall of said nozzle, and means for supplying particles to`be processed to said ports in said member, said dispersion membercausing particles supplied thereto to be discharged as a generallytubular curtain into the space between said nozzle and a flame issuingfrom said burner outlet and causing the said tubular curtain ofparticles to move through said furnace chamber in the same direction asand in encircling relation to the llame and the products of combustionissuing from the burner outlet.

9. A furnace for heat processing particulate solids, especiallyvermiculite, perlite and mixtures thereof, comprising an elongatevertically disposed furnace chamber having an outlet at the lower endthereof, a burner adjacent the upper end of said chamber, said burnerhaving a flame outlet of a size smaller than said chamber directedaxially downward toward said chamber, a particle confining nozzle of asize larger than said burner outlet disposed coaxially within the upperend of said chamber, a dispersion ring disposed concentrically betweensaid burner outlet and said nozzle and having spaced ports thereinopening downwardly into the space between the axial projection of saidburner outlet and the internal wall of said nozzle, a hopper for solidparticles disposed above said chamber and said ring7 and a plurality ofconduits extending downwardly from said hopper to said ports forsupplying particles to be processed to said ports, said burner inoperation discharging'a short llame and products of combustiondownwardly into said nozzle and inducing ow of air and solid particlesthrough said ports in said ring, said dispersion ring causing particlessupplied thereto to be discharged downwardly as a generally tubularcurtain into the space between said nozzle and the llame issuing fromsaid burner outlet, the said curtain of particles gravitating downwardlyas a tubular curtain through said furnace chamber to the chamber outletin 4the same direction as and in encircling relation to the llame andthe products of combustion issuing from the burner outlet, said curtainof particles thereby being disposed between the walls of said nozzle andthe lfurnace chamber and the said llame and products of combustion toinsulate said walls from the source ofl heat and mitigate the occurrenceof hot surfaces on which` the particles could form clnkers.

References Cited in the file of this patent UNITED STATES PATENTS1,854,387 Wickenden Apr. 19, 1932 2,421,902 Neuschotz .lune l0, 19472,621,034 Stecker Dec. 9, 1952

1. A METHOD OF EXPANDING VERMICULITE, PERLITE AND MIXTURES OFVERMICULITE AND PERLITE COMPRISING THE STEPS OF VERTICALLY DROPPING ACURTAIN OF ORE AROUND A HEAT TREATING FLAME, AND CONFINING THE CURTAIN FORE TO THE VICINITY OF AND IN SUBSTANTIALLY ENCOMPASSING RELATION TO THEFLAME AND ITS HOT PRODUCTS OF COMBUSTION DURING VERTICAL DESCENT OF THECURTAIN OF ORE.
 3. APPARATUS FOR HEAT PROCESSING ARTICLATE SOLIDSCOMPRISING A BURNER HAVING A FLAME NOZZLE, A PARTICLE CONFINING NOZZLEDISPOSED TO THE OUTLET SIDE OF SAID FLAME NOZZLE, AND DISPERSION MEANSBETWEEN SAID NOZZLES FOR INTRODUCING A CURTAIN OF THE PARTICLES TO BEPROCESSED ALONG THE WALLS OF SAID CONFINING NOZZLE IN SUBSTANTIALLYENCOMPASSING RELATION TO THE OUTLET OF SAID FLAME NOZZLE.